mirror of
https://github.com/tailscale/tailscale.git
synced 2024-11-29 13:05:46 +00:00
55b1221db2
The packet filter still rejects all IPv6, but decodes enough from v6 packets to do something smarter in a followup. name time/op Decode/tcp4-8 28.8ns ± 2% Decode/tcp6-8 20.6ns ± 1% Decode/udp4-8 28.2ns ± 1% Decode/udp6-8 20.0ns ± 6% Decode/icmp4-8 21.7ns ± 2% Decode/icmp6-8 14.1ns ± 2% Decode/unknown-8 9.43ns ± 2% Signed-off-by: David Anderson <danderson@tailscale.com>
114 lines
2.6 KiB
Go
114 lines
2.6 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package packet
|
|
|
|
import (
|
|
"fmt"
|
|
"net"
|
|
|
|
"inet.af/netaddr"
|
|
)
|
|
|
|
// IP4 is an IPv4 address.
|
|
type IP4 uint32
|
|
|
|
// NewIP converts a standard library IP address into an IP.
|
|
// It panics if b is not an IPv4 address.
|
|
func NewIP4(b net.IP) IP4 {
|
|
b4 := b.To4()
|
|
if b4 == nil {
|
|
panic(fmt.Sprintf("To4(%v) failed", b))
|
|
}
|
|
return IP4(get32(b4))
|
|
}
|
|
|
|
// IPFromNetaddr converts a netaddr.IP to an IP.
|
|
func IP4FromNetaddr(ip netaddr.IP) IP4 {
|
|
ipbytes := ip.As4()
|
|
return IP4(get32(ipbytes[:]))
|
|
}
|
|
|
|
// Netaddr converts an IP to a netaddr.IP.
|
|
func (ip IP4) Netaddr() netaddr.IP {
|
|
return netaddr.IPv4(byte(ip>>24), byte(ip>>16), byte(ip>>8), byte(ip))
|
|
}
|
|
|
|
func (ip IP4) String() string {
|
|
return fmt.Sprintf("%d.%d.%d.%d", byte(ip>>24), byte(ip>>16), byte(ip>>8), byte(ip))
|
|
}
|
|
|
|
func (ip IP4) IsMulticast() bool {
|
|
return byte(ip>>24)&0xf0 == 0xe0
|
|
}
|
|
|
|
func (ip IP4) IsLinkLocalUnicast() bool {
|
|
return byte(ip>>24) == 169 && byte(ip>>16) == 254
|
|
}
|
|
|
|
// IPHeader represents an IP packet header.
|
|
type IP4Header struct {
|
|
IPProto IPProto
|
|
IPID uint16
|
|
SrcIP IP4
|
|
DstIP IP4
|
|
}
|
|
|
|
const ip4HeaderLength = 20
|
|
|
|
func (IP4Header) Len() int {
|
|
return ip4HeaderLength
|
|
}
|
|
|
|
func (h IP4Header) Marshal(buf []byte) error {
|
|
if len(buf) < ip4HeaderLength {
|
|
return errSmallBuffer
|
|
}
|
|
if len(buf) > maxPacketLength {
|
|
return errLargePacket
|
|
}
|
|
|
|
buf[0] = 0x40 | (ip4HeaderLength >> 2) // IPv4
|
|
buf[1] = 0x00 // DHCP, ECN
|
|
put16(buf[2:4], uint16(len(buf)))
|
|
put16(buf[4:6], h.IPID)
|
|
put16(buf[6:8], 0) // flags, offset
|
|
buf[8] = 64 // TTL
|
|
buf[9] = uint8(h.IPProto)
|
|
put16(buf[10:12], 0) // blank IP header checksum
|
|
put32(buf[12:16], uint32(h.SrcIP))
|
|
put32(buf[16:20], uint32(h.DstIP))
|
|
|
|
put16(buf[10:12], ipChecksum(buf[0:20]))
|
|
|
|
return nil
|
|
}
|
|
|
|
// MarshalPseudo serializes the header into buf in the "pseudo-header"
|
|
// form required when calculating UDP checksums. Overwrites the first
|
|
// h.Length() bytes of buf.
|
|
func (h IP4Header) MarshalPseudo(buf []byte) error {
|
|
if len(buf) < ip4HeaderLength {
|
|
return errSmallBuffer
|
|
}
|
|
if len(buf) > maxPacketLength {
|
|
return errLargePacket
|
|
}
|
|
|
|
length := len(buf) - ip4HeaderLength
|
|
put32(buf[8:12], uint32(h.SrcIP))
|
|
put32(buf[12:16], uint32(h.DstIP))
|
|
buf[16] = 0x0
|
|
buf[17] = uint8(h.IPProto)
|
|
put16(buf[18:20], uint16(length))
|
|
return nil
|
|
}
|
|
|
|
// ToResponse implements Header.
|
|
func (h *IP4Header) ToResponse() {
|
|
h.SrcIP, h.DstIP = h.DstIP, h.SrcIP
|
|
// Flip the bits in the IPID. If incoming IPIDs are distinct, so are these.
|
|
h.IPID = ^h.IPID
|
|
}
|